1. Field of the Invention
The present invention relates to a carburetor for adjusting and controlling a concentration and an amount of a mixture supplied toward an engine, and more particularly to an acceleration apparatus of a carburetor for injecting and supplying a fuel for acceleration into an inner portion of an intake passage from an acceleration pump at a time of suddenly opening a throttle valve.
2. Description of the Prior Art
A description will be given of an acceleration apparatus of a carburetor in accordance with a conventional art. A throttle valve operating shaft is rotatably supported to a main body of the carburetor, a throttle lever is fixed and arranged to an end portion thereof, and the throttle lever is connected to an acceleration grip via an acceleration wire. Accordingly, when the acceleration grip is rotated by a driver, the throttle lever rotates in accordance therewith so as to rotate the throttle valve operating shaft, so that the throttle valve connected to the throttle valve operating shaft opens and closes the intake passage. Further, the structure is made such that a cam lever having a cam surface is fixed and arranged to the throttle valve operating shaft, and the cam lever is structured such as to synchronously rotate with the throttle valve operating shaft. An acceleration pump operating shaft is further supported to the main body of the carburetor, and an acceleration operating lever is fixed and arranged to the acceleration pump operating shaft. The acceleration operating lever is structured such as to synchronously rotate with the acceleration pump operating shaft, and the acceleration operating lever is provided with an engagement portion brought into contact with the cam surface of the cam lever and is engaged with an upper end of a pump rod for pressing a diaphragm of the acceleration pump. In this case, when the acceleration grip is rotated and the throttle valve operating shaft rapidly rotates in an opening direction of the throttle valve, the cam surface of the cam lever rotates the acceleration operating lever via the engagement portion, whereby the pump rod presses the pump diaphragm so as to compress a pump chamber, thereby injecting and supplying a desired fuel for acceleration into the inner portion of the intake passage.
In the conventional acceleration apparatus mentioned above, the acceleration operating lever for operating the pump rod is structured such that the engagement portion of the acceleration operating lever is brought into contact with the cam surface of the cam lever, where by a rotational force is applied. Here, paying attention to the cam surface and the engagement portion of the acceleration operating lever, the cam surface of the cam lever moves along the engagement portion of the acceleration operating lever while being brought into contact therewith. On the other hand, a contact portion between the cam surface of the cam lever and the engagement portion of the operating lever is not protected against outside by a protecting member. In accordance with the structure mentioned above, there is a risk that a fine foreign stuff is meshed with the contact portion, whereby there is a risk that the cam surface of the cam lever or the engagement portion of the operating lever corresponding to the contact portion is abraded at a long time use, so that it is hard to obtain a stable operating stroke of the pump diaphragm for a long time and it is hard to stably supply a fuel for acceleration to the engine for a long time. There is a case that the problems mentioned above are generated in a two-wheeled vehicle, an agricultural machine or the like in which the carburetor is directly exposed to outside.
The present invention is made by taking the problems into consideration, and an object of the present invention is to provide an inexpensive acceleration apparatus of a carburetor which can stably supply a fuel for acceleration for a long time.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided an acceleration apparatus of a carburetor comprising:
a throttle valve for opening and closing an intake passage extending through a main body of a carburetor;
a throttle valve operating shaft rotatably supported to a supporting boss of the main body of the carburetor, having a throttle lever mounted at an end portion thereof, and opening and closing the throttle valve;
a cam lever fixed to a throttle valve operating shaft disposed between the throttle lever and the end portion of the supporting boss and provided with a cam surface;
an acceleration pump operating shaft stood from the main body of the carburetor;
a first lever rotatably pivoted to the acceleration pump operating shaft and brought into contact with the cam surface of the cam lever by a first spring for urging in a first rotational direction; and
a second lever rotatably pivoted to the acceleration pump operating shaft, brought into contact with a restriction portion of the first lever by a second spring for urging in a second rotational direction, and arranged in such a manner as to be brought into contact with a pump rod for pressing a pump diaphragm of a pump apparatus,
wherein a contact portion of the first lever brought into contact with the cam surface of the cam lever is arranged between the throttle lever and the end portion of the supporting boss in a direction of a longitudinal axis of the throttle valve operating shaft and within a projected plane of the throttle lever on a surface perpendicular to the longitudinal axis of the throttle valve operating shaft.
Since the cam surface of the cam lever and the contact portion of the first lever are arranged between the throttle lever and the end portion of the supporting boss and within the projected plane of the throttle ever, it effectively prevents a foreign stuff from being attached to the contact portion from outside, whereby it is possible to reduce a sliding friction between the cam surface of the cam lever and the contact portion of the first lever and it is possible to stably supply a fuel for acceleration for a long time.